Hydraulic brake fluid



HYDRAULIC BRAKE FLUID Original` Filed July 26, 1930 INVENTOR- @NDEEW 77K Ziff/VG ATTORNEYS.

Patented Feb. 5, 1935 HYDRAULIC BRAKE FLUID Andrew T. K. Tseng, New York, N. Y., assignor to Hydraulic Brake Company. Detroit, Mich., a corporation of California Original application JuLv 26, 1930, Serial No. 471,048. Divided and this application March 23, 1934, Serial No. 716,991.

Claims.

This invention relates to fluid compositions and more particularly to iluid compositions for use in fluid pressure systems such as hydraulic brakes.

This application is a division of my pending ap- 5 plication Serial Number 471,048, iiled July 26,

1930, and is made in accordance with requirements of the United States Patent Oflice under provision of Rule 42. i

An object of my invention is to provide a brake fluid which will not attack the rubber or metal parts of a brake system.

Another object is to provide a brake fluid which will not volatilize in use. l

Another object is to provide a brake fluid which has an extremely low rate of evaporation.

Another object is to provide a brake fluid which will leave a protective coating on the parts of -the brake system.

Another object is to provide a brake iluid which has a low freezing point.

Another object is to provide a brake uid which has a substantially uniform viscosity between its freezing and boiling points..

Other objects of the invention will appear from the following description taken in connection with the accompanying drawing which forms a part of this specification, and in which,-

Figure 1 is a graphic formula of the furane ring per se; and v Figures 2, 3, 4 and 5 are the graphic formulas of the more important furane ring compounds comprehended in my invention.

It is important that the iiuid be of such character that it will not attack any of the metals used in the various parts of the brake system. It is of utmost importance that the fluid should not attack the rubber of the exible hose or the rubber packing cups employed in the system. 'Ihe latter is particularly essential as any swelling or other deterioration of these packing cups would seriously interfere with the operation of the system.

It is also importantthat the iluid have a sumciently high temperature of vaporization to withstand high temperatures resulting from prolonged application of the brakes without vaporization,

, as vaporization of the brake fluid would create gas or group of elements for one or more of the hydrogen atoms of furane.

With the present knowledge of chemical processes for the manufacture of furane ring compounds, furfural aldehyde is by far the cheapest furane ring compound now obtainable and for this reason alone itis at present the most practical furane ring compound brake fluid. Furfuryl alcohol, furfural acetate, and numerous other furane ring compounds are equally well adapted for use as brake fluids and vmany of lthese furane ring compounds, such as furfuryl alcohol, furfuryl acetate, and several others, are even better adapted for brake iiuid use than is furfural aldehyde because of their lower freezing temperatures.l

It has been found that what is known commercially as technical furfural aldehyde will withstand a temperature of minus 60 F. without freezing, regardless of the length of exposure to such temperature. This is a sufficiently low freezing point for ordinary conditions but vehicles using hydraulic brake systems are sometimes subjected to lower temperatures than minus 60 F. In order to provide a brake fluid which will withstand temperature lower than minus 60 F., it is necessary to add what may be termed a dilutent to furfural aldehyde in order to lower its freezing point. Wherever the word dilutent is used in this specication, it is to be understood as meaning a substance which is added ,solely vfor the purpose of reducing the freezing temperature and has no signicance whatsoever in so far as the vis- 'cosity of the base substance is concerned. Many substancesare suitable for use as dilutents but the following substances are thoughtto be best suited for such use at the present time: ethylenedichloride, diethylene glycol, ethylene glycol,

monoethylether ethylene glycol, `monoethylether diethylene glycol, ethyleneglycolmonoethylether acetate, diethylene oxide, ethyleneglycolmonobutylether, monoacetate glycol, butyl ether diethylene glycol, furfuryl alcohol, furfuryl acetate, propyl furoate, methyl furoate, ethyl furoate, butyl foroate,.butyl alcohol; diacetone alcohol.

A desirable brake fluid has a. rate of evaporation-much lower than that dictated by ordinary usage in a brake system of a motor vehicle in operation so that the fluid may be used to provide a coating which will protect the surfaces of such parts for replacement and repair against corrosion even after practically all of the'brake iluid has evaporated.

Therefore, while furfuralaldehyde evaporates very slowly it is found desirable to add a substance which will still further retard the rate of evaporation and which will increase the protective coating left on the parts after substantially all of the brake fluid has evaporated. ,Bub-

stances added for this purpose are referred to herein as retardants.

certain parts of the system such cylinders and reservoir, including the master cyllate, furiuryl acetate, furfuryl alcohol, methyl furoate, propyl furoate, ethyl furoate, butyl furoate.

It should be noted that several substances are listed both as dilutents and retardants since such substances have the triple characteristicsof reducing the rate of evaporation, lowering the freezing point, and improving the protective coating which is left as a residue on the parts exposed te ine brake nuid. i

Diethylene gLvcol is included'in the 'above lists of dilutents and retardants in spite of the iact that this substance attacks iron and steel. Where diethylene glycol is used it is contemplated that as the wheel inder therein, are die castings, the usual-diecast metal being a non-ferrous alloy of zlnc, tin.

magnesium, aluminum and lead. In such a system the springs in the cylinders could be either brass springs or steel springs coatedwith nickel or chromium. Such a non-ferrous brake system is entirely 'practical from a commercial standpoint, with the present improved process and reduced cost of die-casting.

As previously pointed out, furi'uriil aldehyde alone is an entirely satisfactory brake huid for ordinary operating conditions 'Ihe following specific examples of brake fluids comprising furfural aldehyde mixed-with substances which lower its freezing point, reduce its rate of evapora-f tion end improve the protective coating left as a residue on the parts of brake systems, are typical examples of what may be considered as universal brake fluids capable of fulillling all conditions.

Per cent Furfural aldehyde '10 to 90 Furiuryl alcohol 10 to 30 w n l Per cent Furiural aldehyde approximately 'I8 Furfuryl alcohol. -approximately 20 Cyclo-hexane] approximately 2 Per cent Furiural aldehyde 50 to l0 Diethylene glycol .30 to 50 wniieinsve deceased my invention in demi asappliedtohydraulicbrake,itistobe understood that some features of my invention are equally applicable to hydraulic power trans- 4missionmeansotherthanthatusedinthe application of brakes.

' In this specitlcationthe chemical term iurane ring compoun is used to describethe various chemical compounds which are commonly known in commercial parlance as furiural derivatives A because of the fact that "furfural", (as furfural aldehyde is known is the basis from which all other furane ring compounds are obtained by the present commercial processes.

-while the preferred embodiments or the invention havebeen described in detail, it is not my intention to limit the scope of the invention to the particular embodiments, or otherwise than by the terms oi' the appended claims.

WhatIclaimanddesiretosecurebyUnited States Letters Patent is:

1. A solution for the hydraulic transmission of power including Iurfursl aldehyde and glycol-A monoacetate.

2. A solution for the hydraulic n power comprising furfural aldehyde and diethyleneglycolmonobutylether.

3. A solution for the hydraulic n w of power comprising furfural aldehyde, glycolmonoacetate and diethyleneglycolmonobutylether.

4. A solution for thehydraulic n power comprising avfurane ring compound andf an acetate.

5. A solution for the hydraulic transmission of power comprising a iuranel ring compound and butyl ether diethylene glycol.

ANDREW 'i'. K. Telmo. 

